Physicists at the University of Michigan think they've discovered a new way of sourcing solar energy, that doesn't need expensive semiconductors and solar cells. In the process, they've inadvertently overturned a century-old principle of physics.
Light, like all other physical forces, has electric and magnetic effects. Until now it was thought that the magnetic properties of light were so weak and that they would be useless in any practical application. But what Stephen Rand, the university's professor of applied physics, discovered was that at the right intensity, and when light is travelling through a non-conductive material, the isolated magnetic properties were enhanced significantly.
Suddenly, the light field can generate magnetic effects that are 100 million times stronger than previously expected. Under these circumstances, the magnetic effects have enough strength to generate a strong electric effect.
Rand, who is an author of the research paper, published in the Journal of Applied Physics, said, "You could stare at the equations of motion all day and you will not see this possibility. We've all been taught that this doesn't happen. It's a very odd interaction. That's why it's been overlooked for more than 100 years."
It's all about optical rectification, where light's electrical field causes the positive and negative charges of a material to be forcibly tugged apart, causing an electrical charge.
This had only ever been seen in crystalline materials that possessed a certain symmetry.
But under the right circumstances and with non-conductive materials, light's magnetic field can create optical rectification in something as commonplace as glass.
"It turns out that the magnetic field starts curving the electrons into a C-shape and they move forward a little each time," said William Fisher, a doctoral student in applied physics. "That C-shape of charge motion generates both an electric dipole and a magnetic dipole. If we can set up many of these in a row in a long fibre, we can make a huge voltage and by extracting that voltage, we can use it as a power source."
There's one huge caveat at the moment: the light must be focused to an intensity of 10 million watts per square centimeter.
That's more military-grade laser than the Sun. But Fisher says that new materials that would work at lower intensities are being developed.
Otherwise, the breakthough in solar technology could lead to all-new solar cells that are as powerful as thin film solar panels, but much cheaper. With improved materials, Rand and Fisher believe they could achieve 10 percent efficiency in converting solar power to useable energy. That's equivalent to today's commercial-grade solar cells.
But they wouldn't have to create solar cells which require extensive semiconductor processing -- an expensive and arduous task. "All we would need are lenses to focus the light and a fibre to guide it," says Fisher. "Glass works for both. It's already made in bulk, and it doesn't require as much processing. Transparent ceramics might be even better."
Typical solar cells work by absorbing light into the material, which creates heat. With this new technique, intense magnetisation can be induced by intense light, which is ultimately capable of providing a capacitive power source.
To further their experiments, Rand and Fisher will work on harnessing this power with laser light this summer, and then with sunlight in the future.
This article was originally published by WIRED UK
